Add tasks for all the new languages

Task/Repeat-a-string/Swift/repeat-a-string-3.swift

@@ -0,0 +1,19 @@
+extension String {
+  func repeatBiterative(count: Int) -> String {
+        var reduceCount = count
+        var result = ""
+        var doubled = self
+        while reduceCount != 0 {
+            if reduceCount & 1 == 1 {
+                result.appendContentsOf(doubled)
+            }
+            reduceCount >>= 1
+            if reduceCount != 0 {
+                doubled.appendContentsOf(doubled)
+            }
+        }
+        return result
+    }
+}
+
+"He".repeatBiterative(5)